The present invention relates to an automatic centering device for a conveyor belt for industrial and/or agricultural machinery, in particular for applications in which the material processed by the machine must be carried by the belt at high speed. In many industrial machines (such as mills or similar machines), and in agricultural machinery dedicated, for example, to harvesting, sifting or selecting agricultural products, the conveyor belts used are of the type which are looped around two cylindrical tensioning rollers substantially parallel to one another, one of which may transmit motion to the belt. The belt and the rollers are normally protected by a guard which surrounds the space enclosed by the belt at least as far as the edge of the belt. The conveyor belt normally has ribs transversal to the direction of motion, which allow or increase the efficiency of the transfer of material and can be used to stiffen the belt. Such ribs normally stop at a given distance from the edges of the belt, to allow the space enclosed by the belt to be effectively protected from dust and dirt by means of protective straps fixed to the guard and sliding on the belt.
Conveyor belts of this type are also and in particular used in mowing machines which are self-propelled, towed or drawn by means of transport such as tractors or others, in order to accumulate the mown material on one side or at the center of the mowing machine during movement of the latter.
Due to the particular conditions to which it is subject during operation, the conveyor belt often tends to move sideways towards one end or the other of the tensioning rollers, and is no longer centered. The causes of this behavior by the belt may lie in the high speed of the belt or the vibrations to which the belt is subject during machine operation, in particular caused by the machine transmission mechanisms, or by movement over rough ground in the case of a machine which is self-propelled, towed or drawn by another means. Another cause may be the infiltration of impurities between the roller and the belt, which may promote the transversal sliding of the belt during operation. Moreover, when the machine is moving over the ground, the belt easily loses its centering due to gravity, when the machine moves over sloping ground.
The sideways movement of the belt during operation produces many disadvantages. The loss of optimum positioning may lead to machine operating faults or increased pollution (from dust or other substances) of the space enclosed by the belt. Moreover, it can cause the edges of the belt to rub against parts of the guards, with a consequent rapid deterioration in the conveyor belt due to the high operating speed (in many cases, for example in the case of agricultural mowing machines, the belt speed may reach values of around 400 meters per minute).
In an attempt to avoid these problems, the operator would have to make frequent stops to manually center the belt again.
There are known conveyor belts for agricultural mowing machines which operate at high speed, in which the transversal ribs are extended as far as the edges of the belt. On both sides of the belt there are guides which, at the center of the upper (or lower) course of the belt extend from the guard towards the edge of the belt to make contact with the ends of the ribs if the belt moves transversally.
This type of solution allows a substantially guided belt movement, reducing its transversal movements. However, it does not solve the problem of belt wear due to rubbing on the guides although, to reduce the problem, the ribs used are made of a material which is stiffer than that used to make the belt. Moreover, this solution does not allow effective protection of the space enclosed by the belt from dust and dirt, since the ribs, extending as far as the edge of the conveyor belt, keep any protective straps present raised above the edge.
The aim of the present invention is to overcome the above-mentioned disadvantages by providing an automatic centering device for a conveyor belt for industrial and/or agricultural machinery, which allows the automatic detection of any movement by the conveyor belt from its optimum position and real time implementation of belt position correction without the need for operator intervention.
Another aim of the present invention is to provide an industrial and/or agricultural machine equipped with the automatic centering device for a conveyor belt which, amongst other things, comprises an efficient system for preventing dirt and impurities from entering the space inside the conveyor belt.
A further aim of the present invention is to provide an industrial and/or agricultural machine which comprises an efficient system for preventing dirt and impurities from entering the space inside the conveyor belt.
Accordingly these aims and others, which become clearer in the description which follows, are fulfilled, according to the invention, by an automatic centering device for a conveyor belt for industrial and/or agricultural machinery and by an industrial and/or agricultural machine as described in the claims herein.